The invention relates to woven high frequency transmission cables and more particularly to the shielding of such cables from external high frequency electrical noises such as RF noises which affect the signals being transmitted by the cable. Shielded cable assemblies are also utilized to reduce the noise emitted from the cable itself in order to interfere with surrounding circuitry or electrical devices such as to reduce the hazard of electrical noises interfering with pacemaker devices implanted in heart patients.
In the past, aluminum foil and other similar metals have been used to provide a jacket or sheath which surrounds the transmission in order to reduce the incoming and outgoing noises.
Various arrangements have been provided for draining the high frequency electrical noises from the shield such as soldering a pigtail to the uninsulated side of the jacket. Other means provided have been the laying of an uninsulated conductor wire along the length of the cable sandwiched between the jacket and the cable to drain the noises from the shield. However, the single drain wire does not contact both sides of the shield jacket. This results in increasing the shield's complex impedance which effectively repulses the ability of the shield to adequately drain high frequency noise. In the pigtail connection, considerable amount of time is involved in the process of making the soldered pigtail connection. The connection is also highly susceptible to becoming loose whereby the shield is not drained effectively.
Of the aforementioned types, U.S. Pat. Nos. 4,281,211 and 3,582,532 disclose a metal foil sheath which is drained by a pigtail connector. U.S. Pat. Nos. 4,268,714 and 3,794,750 disclose drain wires in continuous contact with a metal shield.
Accordingly, an important object of the present invention is to provide a shielded woven cable assembly having improved drainage for the shield.
Still another important object of the present invention is to provide a shielded woven cable having drain wires which are terminated in a simple and convenient manner and which provides an effective shield for all applications.
Still another important object of the present invention is to provide a means for draining a shielded woven cable in which the drain is constructed with the woven cable and does not require a separate drain wire or other means for draining the shield.
Still another important object of the present invention is to provide a method for terminating and draining a shield for a woven cable assembly wherein the drain for the shield is woven as integral cable structure with the woven cable.
Another important object of the present invention is to provide a means for selectively isolating certain portions of a cable from noise generated in other sections of the cable by selectively arranging drain wires in the cable which make electrical connection with a shielded jacket surrounding the cable.